The principal function of fins and keels is to regulate and stabilize the course of a craft as it slices through water against lateral wind forces and water currents. During a tacking maneuver or change of course, a fin tends to counteract the effect of the rudder or other turning forces. The number, shape and size of fins must therefore be tuned to the other characteristics of the craft in order to achieve a satisfactory compromise between stability and maneuverability.
The invention results from an attempt to maximize the stabilizing property of a fin without impairing, but rather improving the maneuverability of the craft.
Fins and keels must have a strong longitudinal rigidity. Consequently they are made of solid material having no buoyancy and tend to increase the weight of the craft to which they are appended. The invention also results from efforts to reduce the weight and increase the buoyancy of such appendages.